feat: support Rspack 2 alongside Rspack 1

[dannyhw]

Summary

Tracks Rspack 2 support on a dedicated feature branch while keeping Rspack 1 and webpack working from the same Re.Pack release.

Incremental implementation PRs merge into dannyhw/rspack-2-support after their own review. When one change depends on another, it targets that prerequisite PR first; once the prerequisite lands, the dependent PR is retargeted toward the feature branch. The complete feature is verified here before this draft PR merges to main.

Technical design: agent_context/rspackv2-jul2026/design.md.

Current feature-branch state

Only the first implementation step has landed so far:

• feat: add rspack version detection helpers #1394 — Rspack version-detection helpers and the related configuration keys.

The remaining work has been reduced to four implementation PRs without folding it wholesale into this branch:

• feat: add Rspack 2 runtime foundations and dual-major test infrastructure #1397 — runtime foundations, Rspack 2 types, and dual-major test infrastructure (absorbs feat: add rspack 2 types and dual-major test infrastructure #1398).
• feat: add Rspack 2 config and cache compatibility #1401 — version-aware config and cache compatibility (absorbs feat: warn about legacy experiments.cache config under rspack 2 #1399).
• feat: restructure react refresh support for rspack 2 #1402 — React Refresh compatibility.
• test: add dual-major Rspack compatibility validation #1404 — built-dist smoke coverage and per-major tester apps (absorbs chore: per-major tester apps for the rspack 2 dual-support window #1403).

#1401 and #1402 currently target prerequisite #1397. #1404 remains on the temporary integration base until its implementation prerequisites have landed, then it will retarget to this feature branch.

Delivery flow

1. Review and merge a bounded implementation PR into this feature branch, or into a prerequisite PR when ordering requires it.
2. Retarget dependent PRs as their prerequisites land.
3. Verify the combined feature branch after each merge.
4. Merge this draft feature PR to main only after the full Rspack 1, Rspack 2, and webpack validation matrix passes.

Validation

The current foundations-only feature branch passes:

• pnpm install --frozen-lockfile
• pnpm turbo run typecheck test --force — 17/17 tasks
  • Re.Pack: 30 suites / 290 tests
  • Integration: 58 tests
  • Tester app: 12 tests

#1394 also passed its GitHub Lint, TypeScript, Tests, CodeQL, and Vercel checks before merging.

Broader dual-major validation will be recorded here as later steps land.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 564dbb9

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
repack-website	Ready	Preview, Comment	Jul 26, 2026 8:22pm

[github-actions]

This pull request has been marked as stale because it has been inactive for 30 days. Please update this pull request or it will be automatically closed in 14 days.

[dannyhw]

this is kept for reference but will be revisited soon for v6